Optical components, e.g., assemblies and sub-assemblies of optical telecommunication systems, may be constrained to small packages by design requirements or system performance or cost objectives. Typical of such size-constrained optical components, for example, are certain transmitter optical subassemblies (TOSAs), receiver optical subassemblies (ROSAs) (TOSAs and ROSAs being referred to here also as OSAs), and the like. A TOSA typically includes a laser chip to convert electrical signals into corresponding optical signals passed to an output port coupled (i.e., optically coupled) to an optical output fiber. A ROSA typically receives optical signals from an input fiber and converts them to corresponding electrical signals. OSAs and other optical components must efficiently process and communicate optical signals to or from a light source, e.g., an illuminated fiber in the case of a ROSA, and a laser in the case of a TOSA. Coupling efficiency requirements typically are determined by the applicable system specifications. Difficulties often are encountered in attempting to package additional functionality, e.g., power monitoring, frequency (or wavelength) monitoring etc., into size-constrained housings of these and other optical components.
TOSAs include directly modulated lasers (DMLs), such as semiconductor distributed feedback (DFB) DMLs. DML transmitters can enable a compact system with good response to modulation. Optical multi-filter discriminators are disclosed in co-pending U.S. patent application Ser. No. 60/755,614, filed by Sommer et al. on Dec. 30, 2005 and entitled “Optical Discriminators and Systems and Methods,” the entire disclosure of which is hereby incorporated by reference for all purposes. At least certain embodiments of the multi-filter discriminators disclosed in the Sommer et al. patent application can be used in filtered DML designs, i.e., DMLs having typically two thin film optical filters to improve the signals, e.g., to improve the extinction ration and, so, the travel range of the signals. However, difficulties are encountered in attempting to package additional functionality into the housing or packaging of such filtered DML transmitters. There often is insufficient space in the housing for the laser chip and associated components and filter chips plus beam splitters that could serve to tap off a portion of the optical signal to a photoreceptor (also referred to as photoreceiver) to monitor optical signal power, frequency and/or other properties of the optical signals handled by the TOSA. This may be the case, for example, in a TOSA housing compliant with the Multi-Source Agreement (MSA) of 10 Gbit/s Miniature Device (XMD), XMD04 Physical Interface of LC TOSA Type 2 Package, Rev. 1.2, Jan. 17, 2006. Likewise, packaging difficulties often are encountered in attempting to incorporate additional functionality into the housings of other small optical components. Similarly, it may be difficult to accommodate beam splitters along with the multiple filter chips in optical amplifiers employing multiple gain-flattening filters (GFFs), e.g., in the packaging for multi-chip filter components for gain-flattened optical amplifiers, such as various embodiments of the GFF components disclosed in U.S. patent application Ser. No. 10/874,559, filed Jun. 23, 2004, the entire disclosure of which is hereby incorporated by reference for all purposes.
In these and other applications employing optical filtering, and especially applications using multiple optical thin film filters, it may be difficult to accommodate beam splitters in the optical component's package, e.g., in its specified housing dimensions. It may be difficult or impossible to incorporate beam splitters in such cases even if they were provided as thin film filter chips, in view of the package space limitations.
Accordingly, it is an object of the present invention to provide optical components, devices, systems and methods employing multiple optical filters with dual beam-splitter functionality. In accordance with certain selected aspects of the inventive subject matter disclosed, components, devices, systems and methods are provided for handling (i.e., for generating or processing) optical signals, which employ multiple optical filters together with multiple beam-splitter functionality. Additional objects and features will be apparent to those skilled in the art given the benefit of this disclosure.